For Linux users, pgcedit is also available (it's GPL). But you can't burn the disc as in the guide. Once pgcedit creates the iso and tells you where the layer break sector is:
growisofs -Z /dev/hda=/home/user/image.iso -use-the-force-luke=notray -use-the-force-luke=tty -use-the-force-luke=break:1868912 -dvd-compat -speed=2.4
In this example 1868912 is the layer break sector. Substitute it with yours.
Also in this case /dev/hda is the DVD writer device.
BTW, looking at the command it seems the growisofs programmer is a SW fan
